Cutlass bearing, how old is old?

That's because they do run the engines for long periods in deep water (as you said without sand/silt). Bearings only wear during start up and run down as the shaft is running on a water film and doesn't touch the bearing. Commercial start stop operations in harbours show the highest wear rates (pilot boats in estuaries can be the worst) The latest materials have managed to over come issues for these vessels by reducing wear rates to around a third of that of other materials. There is also the issue of noise and vibration, I guess the Thai fishing boats don't have to conform to noise regulations for working environments?

Fishermen do use QuicKutters http://www.quickwater.com.au/content.htm

 

One problem with high tech cutlass bearings is that you cant source them locally when you need it.

Better to use the common bearings, that are sold locally in every port of the world, then inspect and change as needed.
Changing a well designed shaft bearing installation is a fast easy job and it allows you " NOSE" time, up close and personal to the drive train .

Every Time I inspect a drive train something needs service.

 

I find that many vessels do not have standard sizes as supplied by the old style rubber in bronze bearings. The new materials can also be used as direct replacement for old white metal oil or grease shaft bearings, try getting a 6" white metal replacement it's likely to take a few days to sort in most places. The new composites also don't need presses to fit as they slide in by hand which makes them ideal for yards with limited equipment.



For these it is often very quick to get a composite bearing made to order and shipped direct to the yard. I've done this with ship slipped in Italy on a Friday, shafts/carriers measured and by the following Tuesday new bearings had arrived custom made from Australia.

 

Even better is to carry a spare bearing on the boat...Zero order time !

 

I used vesconite. And they custom cut them and were ~$25 for two I recall. 1 3/8 shafts maybe 6 inch long bushings.
I froze them and pressed them into the struts along with a little grease.

So far they have been fine for the last 5 years.
http://www.vesconite.com/

I actually called and talked to the sales guy in S. Africa.
Got them in an envelope air mailed.